The use of tufting machines to create tufted materials, such as carpet and rugs, is well known in the art. The art of tufting incorporates a plurality of yarn carrying needles extending transversely across the machine. Conventional tufting machines use a reciprocating needle bar, which carries the plurality of needles. The needles are constructed and arranged to reciprocate cyclically beneath the needle bar to penetrate and insert pile into a backing material passing below the same in a longitudinal direction. During each penetration of the backing material a row of pile is produced transversely across the backing. Successive penetrations result in a longitudinal row of pile produced by each needle.
The amount of tufted goods that can be produced by any given machine is often limited by the speed of the tufting machine. Therefore, the speeds of tufting machines have increased substantially throughout the development of the tufting art. As the speeds of tufting machines have increased to over 2000 rpm, it has been discovered that many of the moving parts tend to wear increasingly fast, and additionally, it has been found that the needle bar can crack and break due to the excessive vibration caused by such high speeds. Unfortunately, needle bars are very expensive to replace in terms of both money and machine downtime. Furthermore, it has been found that vibration damage is even more likely to occur when a shifting needle bar arrangement is used to create patterns in the tufted goods.
To combat vibration damage that occurs at high speeds, cam follower brackets 10, as seen in FIGS. 1-3, have been used in the art to dampen the vibrations at the needle bar due to the tufting machines' high-speed vertical reciprocating motion. Known cam follower brackets are typically mounted to the tufting machine's Thompson rods/bars 20 and are traditionally equipped with two cam follower bearings 30. The bearings 30 are forced against both sides of an elongated shifter block 40, which is coupled to the top of the needle bar 50. As the needle bar 50 and shifter block 40 vertically reciprocate, pressure applied by the bearings 30 onto the shifter block 40 helps prevent the needle bar from vibrating. Over time however, the cam follower bearings 30 and shifter block 40 begin to wear. Therefore, a user must periodically tighten the bearings 30 against the shifter block 40 to maintain an adequate pressure against the same.
Presently, there are two known types of cam follower brackets that are used in the art. The first type is that shown in FIG. 2, which utilizes bearings 30 having an eccentric shaft 35. The shaft 35 can be turned within a substantially cylindrical bore 15 of the bracket 10′, such that more or less pressure is applied against the shifter block 40. A user can then bolt the bearing 30 in place when the desired level of pressure against the block 40 has been achieved. The second type of cam follower bracket 10, as seen in FIG. 3, has an elongated cylindrical bore 15, within which the bearing shaft 35 horizontally slides. To tighten the bearing 30 against the shifter block 40 a setscrew 38 is utilized to force the bearing against the same.
Unfortunately, when a user utilizes either of the arrangements as discussed above, the user must continuously monitor the bearings' 30 configuration to make sure that the appropriate amount of force is being applied to the shifter block 40. Too much pressure can cause the needle bar 50 to crack and break, while too little pressure can cause excessive needle bar vibration. Additionally, neither of the aforementioned cam follower brackets 10 and 10′ are well suited for uneven bearing 30 and shifter block 40 wear, which is a very typical problem. For example, once a bearing 30 or shifter block 40 begins to wear unevenly, the needed amount of bearing pressure against the block can vary widely over the course of one reciprocating cycle. Presently, known brackets only permit one constant pressure, which can cause further uneven wear and damaging vibrations.
Thus it can be seen that needs exist for improvements to cam follower brackets to minimize the amount of user monitoring and permit a variable range of bearing pressure against the shifter block. It is to the provision of these needs and others that the present invention is primarily directed.